text: Target screening or analysis is useful when looking for a short list of predetermined organic compounds in a sample, while ignoring other compounds that may be present. Reference standards that align with the predetermined compounds are available and used to compare attributes such as chromatographic retention time, fragmentation pattern, and isotopic pattern. The workflow for target screening requires the optimization of sample extraction, sample clean-up, and instrumentation methods to those predetermined compounds in order to achieve "a specific and accurate measurement." Most analytical results will be quantitative in nature, given the narrow focus of screening. As such, targeted approaches have traditionally been used in regulatory monitoring schemes. The downside, however, is that many hazardous organic compounds are not covered by environmental monitoring regulation and thus not specifically targeted, and the approach is not generally adept for rapid response approaches to providing early warning of contamination events.